The exhaust units used in food preparation and commercial kitchens include devices such as air extractor hoods and air conditioning units. The traditional exhaust systems include filter elements that use a variety of metal or flame listed baffles, as identified in the various U.S. or State Codes, for the purpose of blocking flames from penetrating the exhaust system and diverting grease from building up in the ductwork of the exhaust system.
The exhausted air in the food preparation environment is typically laden with greasy vapor and unwanted odors and substances. The grease and unwanted substances should be trapped by the filters before passing through to the ducting to be released to the environment. Grease may collect on ductwork or pass into the environment. In addition, the grease and others substances contaminate the hood and fan and these require constant cleaning to remove the grease. As the filters get quickly filled with grease they require regular cleaning. Moreover, the grease in the ducting constitutes a major fire hazard as ducting fires are a constant concern.